Few energy industry practices have sparked more controversy than hydraulic fracking. First, wells are drilled horizontally below the surface, allowing a single bore or pathway to reach vertical pockets of oil and natural gas trapped between formations of shale and other rock. Then high-pressure jets of water, sand, and chemicals are pumped into the ground to create fissures through the rock so oil can seep out and be retrieved. Regulators, environmentalists, and academics are studying whether the practice can damage the environment.
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